Consumer markets continue to request smaller, portable electronic devices which have greater functional features. Examples of such devices include two-way and broadcast radio receivers, compact disc players, cellular telephones, and computer devices, to name but a few. As portable electronic devices have become smaller, the demand for smaller energy sources, such as batteries, to power such devices has increased. Obviously very small energy storage devices, such as an electrochemical battery cell, may be fabricated for a given electrical device, but compactness comes at the cost of energy capacity. Accordingly, for many high power applications the energy source is too bulky, too heavy, or doesn't last long enough.
One limiting feature of current battery cells is the packaging of the electrochemical system. The current convention is to house the electrodes and electrolyte in a cylindrical or square (prismatic) steel can. This form of packaging is widely commercially available. In the past this has forced designers to design electrical products around the cells, rather than design the product the way they would prefer, adding the energy source later.
Further, as the physical size of batteries decreases (to meet size requirements of product designers), the capacity of the battery is reduced. This results in device users needing many batteries if they anticipate being away from a battery charging device for extended periods of time. Alternatively, users may carry portable, high speed, charging devices with them. This however is unacceptable, due to the additional weight associated with the charging device.
To address this problem, many devices now include battery chargers formed integrally therewith. These systems avoid the problems associated with carrying a discrete charging device, however still require the user to carry a charging cord, and have access to a power source, such as a wall plug. Alternatively, and under appropriate conditions, energy sources such as photovoltaic cells may be incorporated into the housing of electronic devices. A common example of such a device is battery powered walk lights which are commercially available. Such devices include a conventional battery in a steel can, which is electrically interconnected to a photovoltaic cell for recharging. The drawback to this approach is that the design of the walk light is constrained by both the size and shape limitations of the cell can, and the requirements for a large, fiat area for the photovoltaic cell.
Accordingly, what is needed is a means to reduce the bulkiness of the energy source, such as a battery, necessary for use with small, electronic devices. The energy source should be small, conformal, relatively flexible, and able to provide an appropriate housing for the electronic device associated therewith. The energy source should also include an integrally formed recharging device, which is free from the limitations of the prior art.